| 1. |
- Berggren, Magnus, 1968-, et al.
(författare)
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Organic laser based on lithographically defined photonic-bandgap resonators
- 1998
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Ingår i: Electronics Letters. - : IEEE. - 0013-5194 .- 1350-911X. ; 34:1, s. 90-91
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Tidskriftsartikel (refereegranskat)abstract
- The authors report the fabrication and characteristics of organic solid-state waveguide lasers with feedback from a photolithographically defined rhomboid photonic bandgap lattice. The lattice is formed by etching holes of depth 10-40 nm in SiO2 and filling them with the organic gain medium. The gain medium is part of a planar waveguide formed by air/organic layer/SiO2.
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| 2. |
- Berggren, Magnus, et al.
(författare)
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Organic solid-state lasers with imprinted gratings on plastic substrates
- 1998
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 72:4, s. 410-411
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Tidskriftsartikel (refereegranskat)abstract
- Optically pumped laser emission has been observed from thin films of 8-hydroxyquinolinato aluminum (Alq) doped with a DCM dye deposited on a diffraction,orating formed by imprinting a film of BCB with a mold. The BCB film, which is 4 mu m thick, is deposited on a silicon or a flexible plastic substrate. Laser emission occurs at a wavelength war 655 nm which corresponds to the third order of the grating, which has a periodicity of similar to 0.6 mu m. (C) 1998 American Institute of Physics.
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| 3. |
- Dodabalapur, A, et al.
(författare)
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Resonators and materials for organic lasers based on energy transfer
- 1998
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X .- 1558-4542. ; 4:1, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- Optically pumped lasers have been fabricated with organic/polymeric materials capable of charge transport. The active materials employed are doped films with small molecule hosts and dye, oligomer, and conjugated polymer emitters, In these materials, the excited states created in the host are transferred nonradiatively to the guest molecules which are the emitters, This energy transfer results in very low absorption losses at the emission wavelength and relatively low-threshold powers for the onset of stimulated emission. Such gain media have been successfully included in many types of resonators including whispering-gallery mode, photonic bandgap, and distributed Bragg reflector (DBR) based resonators. A number of novel patterning and fabrication procedures have been developed for organic-based lasers.
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| 4. |
- Trubetskaya, Anna, et al.
(författare)
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Characterization and reactivity of soot from fast pyrolysis of lignocellulosic compounds and monolignols
- 2018
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Ingår i: Applied Energy. - Oxford : Elsevier. - 0306-2619 .- 1872-9118. ; 212, s. 1489-1500
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Tidskriftsartikel (refereegranskat)abstract
- This study presents the effect of lignocellulosic compounds and monolignols on the yield, nanostructure and reactivity of soot generated at 1250 °C in a drop tube furnace. The structure of soot was characterized by electron microscopy techniques, Raman spectroscopy and electron spin resonance spectroscopy. The CO2 reactivity of soot was investigated by thermogravimetric analysis. Soot from cellulose was more reactive than soot produced from extractives, lignin and monolignols. Soot reactivity was correlated with the separation distances between adjacent graphene layers, as measured using transmission electron microscopy. Particle size, free radical concentration, differences in a degree of curvature and multi-core structures influenced the soot reactivity less than the interlayer separation distances. Soot yield was correlated with the lignin content of the feedstock. The selection of the extraction solvent had a strong influence on the soot reactivity. The Soxhlet extraction of softwood and wheat straw lignin soot using methanol decreased the soot reactivity, whereas acetone extraction had only a modest effect.
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| 5. |
- Bellis, Emily S, et al.
(författare)
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Genomics of sorghum local adaptation to a parasitic plant
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:8, s. 4243-4251
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Tidskriftsartikel (refereegranskat)abstract
- Host-parasite coevolution can maintain high levels of genetic diversity in traits involved in species interactions. In many systems, host traits exploited by parasites are constrained by use in other functions, leading to complex selective pressures across space and time. Here, we study genome-wide variation in the staple crop Sorghum bicolor (L.) Moench and its association with the parasitic weed Striga hermonthica (Delile) Benth., a major constraint to food security in Africa. We hypothesize that geographic selection mosaics across gradients of parasite occurrence maintain genetic diversity in sorghum landrace resistance. Suggesting a role in local adaptation to parasite pressure, multiple independent loss-of-function alleles at sorghum LOW GERMINATION STIMULANT 1 (LGS1) are broadly distributed among African landraces and geographically associated with S. hermonthica occurrence. However, low frequency of these alleles within S. hermonthica-prone regions and their absence elsewhere implicate potential trade-offs restricting their fixation. LGS1 is thought to cause resistance by changing stereochemistry of strigolactones, hormones that control plant architecture and below-ground signaling to mycorrhizae and are required to stimulate parasite germination. Consistent with trade-offs, we find signatures of balancing selection surrounding LGS1 and other candidates from analysis of genome-wide associations with parasite distribution. Experiments with CRISPR-Cas9-edited sorghum further indicate that the benefit of LGS1-mediated resistance strongly depends on parasite genotype and abiotic environment and comes at the cost of reduced photosystem gene expression. Our study demonstrates long-term maintenance of diversity in host resistance genes across smallholder agroecosystems, providing a valuable comparison to both industrial farming systems and natural communities.
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| 6. |
- Janáky, C., et al.
(författare)
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Chemical synthesis of poly(3-thiophene-acetic-acid)/magnetite nanocomposites with tunable magnetic behaviour
- 2010
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 160:1-2, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- Conducting polymer-based magnetic composites with controlled magnetic behaviour have been synthesized by chemical polymerization in nanoparticle containing organic media. Poly(3-thiophene-acetic-acid)–Fe3O4 hybrids have been prepared with five different iron-oxide contents, up to 20 m/m%, according to the results obtained by thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectroscopic (ICP-AES) measurements. X-ray diffraction (XRD) and Mössbauer spectroscopic results gave direct evidences for the incorporation of both maghemite and magnetite. Photoacoustic Fourier transform infrared spectroscopic (PAS-FT-IR) measurements showed a chemical interaction between the polymer and the iron-oxide particles. SQUID investigations indicated a typical superparamagnetic behaviour for all samples, where saturation magnetization values proved to be tunable by the Fe3O4 content. After coating them onto electrode surfaces, basic electrochemical activity of the composite samples was demonstrated by cyclic voltammetry.
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| 7. |
- Melet, Angélique, et al.
(författare)
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Internal tide generation by abyssal hills using analytical theory
- 2013
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Ingår i: Journal of Geophysical Research - Oceans. - 2169-9275 .- 2169-9291. ; 118:11, s. 6303-6318
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Tidskriftsartikel (refereegranskat)abstract
- Internal tide driven mixing plays a key role in sustaining the deep ocean stratification and meridional overturning circulation. Internal tides can be generated by topographic horizontal scales ranging from hundreds of meters to tens of kilometers. State of the art topographic products barely resolve scales smaller than ∼10 km in the deep ocean. On these scales abyssal hills dominate ocean floor roughness. The impact of abyssal hill roughness on internal-tide generation is evaluated in this study. The conversion of M2 barotropic to baroclinic tidal energy is calculated based on linear wave theory both in real and spectral space using the Shuttle Radar Topography Mission SRTM30_PLUS bathymetric product at 1/120° resolution with and without the addition of synthetic abyssal hill roughness. Internal tide generation by abyssal hills integrates to 0.1 TW globally or 0.03 TW when the energy flux is empirically corrected for supercritical slope (i.e., ∼10% of the energy flux due to larger topographic scales resolved in standard products in both cases). The abyssal hill driven energy conversion is dominated by mid-ocean ridges, where abyssal hill roughness is large. Focusing on two regions located over the Mid-Atlantic Ridge and the East Pacific Rise, it is shown that regionally linear theory predicts an increase of the energy flux due to abyssal hills of up to 100% or 60% when an empirical correction for supercritical slopes is attempted. Therefore, abyssal hills, unresolved in state of the art topographic products, can have a strong impact on internal tide generation, especially over mid-ocean ridges.
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| 8. |
- Murphy, Kathleen, 1972, et al.
(författare)
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Photochemistry Illuminates Ubiquitous Organic Matter Fluorescence Spectra
- 2018
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 52:19, s. 11243-11250
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved organic matter (DOM) in aquatic environments forms a vast reservoir of carbon present as a complex supermixture of compounds. An efficient approach to tracking the production and removal of specific DOM fractions is needed across disciplines, for purposes that range from improving global carbon budgets to optimizing water treatment in engineered systems. Although widely used to study DOM, fluorescence spectroscopy has yet to deliver specific fractions with known spectral properties and predictable distributions. Here, we mathematically isolate four visible-wavelength fluorescent fractions in samples from contrasting lake, river, and ocean environments. Using parallel factor analysis (PARAFAC), we show that most measured fluorescence in environmental samples can be explained by ubiquitous spectra with nearly stable optical properties and photodegradation behaviors over environmental pH gradients. Sample extraction changed bulk fluorescence spectra but not the number or shape of underlying PARAFAC components, while photobleaching preferentially removed the two longest-wavelength components. New approaches to analyzing fluorescence data sets incorporating these findings should improve the interpretation of DOM fluorescence and increase its utility for tracing organic matter biogeochemistry in aquatic systems.
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